An electronic clinical thermometer, wide-spreading currently, includes a button type battery as a power source and a probe that is brought into contact with axillar or a part under the tongue, so as to detect a change in resistance of temperature-sensitive element (thermistor) placed in the probe, convert the detected value into a temperature value, and display the temperature on a liquid crystal display (LCD), and this type of electronic clinical thermometer is commonly used. This type of electronic clinical thermometer incorporates in a plastic case, a power source battery, a measurement circuit, an LCD, an operating switch, and the like. The probe is formed on one end of the electronic clinical thermometer body, and the probe includes a probe body in which an insertion path for inserting a lead wire connected to the thermistor, and a sensor cap mounted on the probe body. The thermistor is disposed on the inner wall of the sensor cap in such a manner as being in contact therewith, and held on the inner wall with an adhesive filled therein. Such electronic clinical thermometer configured as described above has been proposed so far.    [Patent document 1]    Japanese Registered Utility Model No. 3096508 (Page 9, FIG. 3)    [Patent document 2]    Japanese Unexamined Utility Model Application Publication No. 62-132436 (Pages 3 to 4, FIG. 1)    [Patent document 3]    Japanese Registered Utility Model No. 3094041 (Pages 5 to 6, FIG. 3 and FIG. 4)    [Patent document 4]    Japanese Unexamined Utility Model Application Publication No. 62-170537 (Pages 1 to 4, FIG. 1 to FIG. 3)
As shown in FIG. 15, the electronic clinical thermometer disclosed in the patent document 1 has a temperature probe 31 that includes a probe body 32, and a sensor cap 33 provided with a hollow end that is fastened to the probe body 32. This sensor cap 33 includes a thermal contact surface 33a and a cavity 33b surrounded by the thermal contact surface 33a. The thermistor 34 is fastened to a location of an inner tip 33c of the thermal contact surface 33a of the sensor cap 33. A pair of the lead wire 35 is connected to the thermistor 34 and transmits a temperature signal.
This lead wire 35 includes a part 35a that is fastened to the inside of the thermal contact surface 33a of the sensor cap 33. The leadwire 35 in proximity to the thermistor 34 is not in contact with the inner wall 33c of the sensor cap 33. An intermediate part positioned at a distance from the vicinity of the thermistor 34 is brought into contact with the thermal contact surface 33a of the sensor cap 33.
As shown in FIG. 16, a thermometer probe 41 of the electronic clinical thermometer disclosed in the patent document 2 is configured such that a sensor cap 43 fits into a tip of a tubular probe body 42, and a thermistor 44 is embedded in an adhesive 46 that is encapsulated in the tip of this sensor cap 43. The tip of the thermistor 44 abuts against the inner side of the sensor cap 43.
Lead wire 45 from the thermistor 43 is guided to the probe body 42 side along the inner wall of the sensor cap 43 with the adhesive 46. A part of the adhesive 46 is extended towards the probe body 42 side in a shape of sleeve along the inner wall of the sensor cap 43, and the adhesive 46 is fastened to the inner wall of the sensor cap 43.
With the probe in the electronic clinical thermometer as described above, the heat transferred from a measured part to the sensor cap is further transferred from the sensor cap to the lead wire, and the heat transferred to the thermistor is prevented from being liberated through the lead wire.
As shown in FIG. 17 and FIG. 18, in the electronic clinical thermometer disclosed in the patent document 3, a thermistor 54 and lead wire 55 are disposed inside the sensor cap 53. The thermistor 54 is fixed onto an inner wall of the tip of the sensor cap 53 with an adhesive 56.
One end of the lead wire 55 is connected to the thermistor 54, and the other end is connected to an IC within a case outside the electronic clinical thermometer, not illustrated. A sensor cap 53 is filled with a heat insulator 57 that hardly transmits heat, and the thermistor 54 and the lead wire 55 are fixed securely within the sensor cap 53.
As described above, since the sensor cap is filled with the heat insulator, the entire lead wire within the sensor cap, including a part in proximity to the thermistor, is attached firmly to the inner wall of the sensor cap cavity.
The patent document 4 discloses two electronic clinical thermometers. One of them is shown in FIG. 19 and FIG. 20. In this clinical thermometer, there is formed a locking hook 61a that locks the lead wire 63 connected to the thermistor 62 on the tip of the probe 61, so as to adjust a position of the lead wire in the middle position, the probe 61 storing a circuit board 60 on which circuit components for temperature measurement are implemented, and the locking hook 61a is integrally formed with the probe 61.
This locking hook 61a is formed so that the thermistor 62 abuts against the inner bottom surface of the sensor cap 64 when the sensor cap 64 fits into the probe 61. The thermistor 62 is connected to the lead wire, and fastened to the inner bottom surface of the sensor cap 64 with an adhesive 66. Reference numeral 67 indicates a battery and reference numeral 65 indicates a battery cover.
FIG. 21 shows the other electronic clinical thermometer, and it has the same configuration as the electronic clinical thermometer as shown in FIG. 19 and FIG. 20, except that the lead wire 63 of the thermistor 62 is not locked within the sensor cap 64. The patent document 4 describes a method of producing those electronic clinical thermometers as described above.
In assembling the electronic clinical thermometer as shown in FIG. 19 and FIG. 20, the lead wire 63 of the thermistor 62 is firstly connected to the circuit of the circuit board 60. Subsequently, in the state where the battery 67 and the battery cover 65 positioned in the rear of the probe 61 are removed, the thermistor 62 and the circuit board 60 are inserted from the rear of the probe 61, and the lead wire 63 of the thermistor 62 that appears in the front side of the probe 61 is locked on the locking hook 61a. Then, the front side of the probe 61 is fixed on the sensor cap 64 in which a little amount of adhesive 66 is injected. The probe 61 and the sensor cap 64 are fastened to each other with the adhesive 66. The thermistor 62 comes into contact with the inner bottom surface of the sensor cap 63 and fixed thereon.
In the electronic clinical thermometer as shown in FIG. 21, the lead wire 63 of the thermistor 62 is firstly connected to the circuit board 60, and subsequently, these elements are inserted from the rear of the probe 61. The thermistor 62 is brought into contact with the inner wall surface of the sensor cap 64, and fastened thereto with the adhesive 66.
In the electronic clinical thermometers as described in the patent document 1 and the patent document 2, the lead wire in proximity to the thermistor does not come into contact with the sensor cap. Therefore, there has been a problem that the heat on the thermistor escapes towards the non-contact lead wire, whereby a rise in temperature becomes slower and longer time is necessary for measurement.
In the electronic clinical thermometer as described in the patent document 3, the thermistor to which the lead wire is connected is firstly fixed on the inner wall of the tip of the sensor cap with an adhesive, and thereafter the heat insulator is put within the sensor cap. When the heat insulator is inserted in a state where the lead wire is freely movable, the lead wire may be pressed down towards the inner wall of the sensor cap by the outer surface of the heat insulator, and the lead wire may be dragged and drawn into the sensor cap more than necessary.
If the heat insulator is inserted while a part of the lead wire that projects outwardly from the sensor cap is fixed, to avoid the lead wire from being drawn into the sensor cap, a tensile force is generated on the lead wire and a stress is concentrated at least on a portion of the lead wire between the thermistor and the fixed portion. Therefore, there is a possibility that the lead wire may be broken.
With the structure of the electronic clinical thermometer and a method of producing the same as described in the above patent document 4, it is not possible to firmly attach the lead wire onto the inner wall of the sensor cap. Therefore, there has been a problem that a desired high-speed electronic clinical thermometer cannot be produced.
The present invention has been made to address the disadvantages as described above, and an object of the present invention is to provide an electronic clinical thermometer that can be produced without breaking the lead wire and also effectively prevent dissipation of heat from the thermistor to the lead wire, and further to provide a method of producing this electronic clinical thermometer.